@Nullable
  public static PyType getType(@NotNull PsiElement resolved, @NotNull List<PyType> elementTypes) {
    final String qualifiedName = getQualifiedName(resolved);

    final List<Integer> paramListTypePositions = new ArrayList<>();
    final List<Integer> ellipsisTypePositions = new ArrayList<>();
    for (int i = 0; i < elementTypes.size(); i++) {
      final PyType type = elementTypes.get(i);
      if (type instanceof PyTypeParser.ParameterListType) {
        paramListTypePositions.add(i);
      } else if (type instanceof PyTypeParser.EllipsisType) {
        ellipsisTypePositions.add(i);
      }
    }

    if (!paramListTypePositions.isEmpty()) {
      if (!("typing.Callable".equals(qualifiedName) && paramListTypePositions.equals(list(0)))) {
        return null;
      }
    }
    if (!ellipsisTypePositions.isEmpty()) {
      if (!("typing.Callable".equals(qualifiedName) && ellipsisTypePositions.equals(list(0))
          || "typing.Tuple".equals(qualifiedName)
              && ellipsisTypePositions.equals(list(1))
              && elementTypes.size() == 2)) {
        return null;
      }
    }

    if ("typing.Union".equals(qualifiedName)) {
      return PyUnionType.union(elementTypes);
    }
    if ("typing.Optional".equals(qualifiedName) && elementTypes.size() == 1) {
      return PyUnionType.union(elementTypes.get(0), PyNoneType.INSTANCE);
    }
    if ("typing.Callable".equals(qualifiedName) && elementTypes.size() == 2) {
      final PyTypeParser.ParameterListType paramList =
          as(elementTypes.get(0), PyTypeParser.ParameterListType.class);
      if (paramList != null) {
        return new PyCallableTypeImpl(paramList.getCallableParameters(), elementTypes.get(1));
      }
      if (elementTypes.get(0) instanceof PyTypeParser.EllipsisType) {
        return new PyCallableTypeImpl(null, elementTypes.get(1));
      }
    }
    if ("typing.Tuple".equals(qualifiedName)) {
      if (elementTypes.size() > 1 && elementTypes.get(1) instanceof PyTypeParser.EllipsisType) {
        return PyTupleType.createHomogeneous(resolved, elementTypes.get(0));
      }
      return PyTupleType.create(resolved, elementTypes);
    }
    final PyType builtinCollection = getBuiltinCollection(resolved);
    if (builtinCollection instanceof PyClassType) {
      final PyClassType classType = (PyClassType) builtinCollection;
      return new PyCollectionTypeImpl(classType.getPyClass(), false, elementTypes);
    }
    return null;
  }
 @Nullable
 private static PyType getParameterizedType(
     @NotNull PsiElement element, @NotNull Context context) {
   if (element instanceof PySubscriptionExpression) {
     final PySubscriptionExpression subscriptionExpr = (PySubscriptionExpression) element;
     final PyExpression operand = subscriptionExpr.getOperand();
     final PyExpression indexExpr = subscriptionExpr.getIndexExpression();
     final PyType operandType = getType(operand, context);
     if (operandType instanceof PyClassType) {
       final PyClass cls = ((PyClassType) operandType).getPyClass();
       final List<PyType> indexTypes = getIndexTypes(subscriptionExpr, context);
       if (PyNames.TUPLE.equals(cls.getQualifiedName())) {
         if (indexExpr instanceof PyTupleExpression) {
           final PyExpression[] elements = ((PyTupleExpression) indexExpr).getElements();
           if (elements.length == 2 && isEllipsis(elements[1])) {
             return PyTupleType.createHomogeneous(element, indexTypes.get(0));
           }
         }
         return PyTupleType.create(element, indexTypes);
       } else if (indexExpr != null) {
         return new PyCollectionTypeImpl(cls, false, indexTypes);
       }
     }
   }
   return null;
 }
 @Nullable
 private static PyType getCallableType(@NotNull PsiElement resolved, @NotNull Context context) {
   if (resolved instanceof PySubscriptionExpression) {
     final PySubscriptionExpression subscriptionExpr = (PySubscriptionExpression) resolved;
     final PyExpression operand = subscriptionExpr.getOperand();
     final Collection<String> operandNames =
         resolveToQualifiedNames(operand, context.getTypeContext());
     if (operandNames.contains("typing.Callable")) {
       final PyExpression indexExpr = subscriptionExpr.getIndexExpression();
       if (indexExpr instanceof PyTupleExpression) {
         final PyTupleExpression tupleExpr = (PyTupleExpression) indexExpr;
         final PyExpression[] elements = tupleExpr.getElements();
         if (elements.length == 2) {
           final PyExpression parametersExpr = elements[0];
           final PyExpression returnTypeExpr = elements[1];
           if (parametersExpr instanceof PyListLiteralExpression) {
             final List<PyCallableParameter> parameters = new ArrayList<>();
             final PyListLiteralExpression listExpr = (PyListLiteralExpression) parametersExpr;
             for (PyExpression argExpr : listExpr.getElements()) {
               parameters.add(new PyCallableParameterImpl(null, getType(argExpr, context)));
             }
             final PyType returnType = getType(returnTypeExpr, context);
             return new PyCallableTypeImpl(parameters, returnType);
           }
           if (isEllipsis(parametersExpr)) {
             return new PyCallableTypeImpl(null, getType(returnTypeExpr, context));
           }
         }
       }
     }
   }
   return null;
 }
 @Nullable
 private static PyType getType(@NotNull PyExpression expression, @NotNull Context context) {
   final List<PyType> members = Lists.newArrayList();
   for (PsiElement resolved : tryResolving(expression, context.getTypeContext())) {
     members.add(getTypeForResolvedElement(resolved, context));
   }
   return PyUnionType.union(members);
 }
 @Nullable
 private static PyType getGenericTypeBound(
     @NotNull PyExpression[] typeVarArguments, @NotNull Context context) {
   final List<PyType> types = new ArrayList<>();
   for (int i = 1; i < typeVarArguments.length; i++) {
     types.add(getType(typeVarArguments[i], context));
   }
   return PyUnionType.union(types);
 }
  public PyType getType(@NotNull TypeEvalContext context, @NotNull TypeEvalContext.Key key) {
    if (!TypeEvalStack.mayEvaluate(this)) {
      return null;
    }
    try {
      final boolean qualified = isQualified();
      if (!qualified) {
        String name = getReferencedName();
        if (PyNames.NONE.equals(name)) {
          return PyNoneType.INSTANCE;
        }
      }
      PyType type = getTypeFromProviders(context);
      if (type != null) {
        return type;
      }
      if (qualified) {
        PyType maybe_type = PyUtil.getSpecialAttributeType(this, context);
        if (maybe_type != null) return maybe_type;
        Ref<PyType> typeOfProperty = getTypeOfProperty(context);
        if (typeOfProperty != null) {
          return typeOfProperty.get();
        }
      }
      final PsiPolyVariantReference reference =
          getReference(PyResolveContext.noImplicits().withTypeEvalContext(context));
      final List<PsiElement> targets = PyUtil.multiResolveTopPriority(reference);
      if (targets.isEmpty()) {
        return getQualifiedReferenceTypeByControlFlow(context);
      }

      final List<PyType> members = new ArrayList<PyType>();
      for (PsiElement target : targets) {
        if (target == this || target == null) {
          continue;
        }
        if (!target.isValid()) {
          LOG.error(
              "Reference "
                  + this
                  + " resolved to invalid element "
                  + target
                  + " (text="
                  + target.getText()
                  + ")");
          continue;
        }
        members.add(getTypeFromTarget(target, context, this));
      }

      return PyUnionType.union(members);
    } finally {
      TypeEvalStack.evaluated(this);
    }
  }
 @NotNull
 public QualifiedResolveResult followAssignmentsChain(PyResolveContext resolveContext) {
   PyReferenceExpression seeker = this;
   QualifiedResolveResult ret = null;
   List<PyExpression> qualifiers = new ArrayList<PyExpression>();
   PyExpression qualifier = seeker.getQualifier();
   if (qualifier != null) {
     qualifiers.add(qualifier);
   }
   Set<PsiElement> visited = new HashSet<PsiElement>();
   visited.add(this);
   SEARCH:
   while (ret == null) {
     ResolveResult[] targets = seeker.getReference(resolveContext).multiResolve(false);
     for (ResolveResult target : targets) {
       PsiElement elt = target.getElement();
       if (elt instanceof PyTargetExpression) {
         PsiElement assigned_from = null;
         final PyTargetExpression expr = (PyTargetExpression) elt;
         final TypeEvalContext context = resolveContext.getTypeEvalContext();
         if (context.maySwitchToAST(expr) || expr.getStub() == null) {
           assigned_from = expr.findAssignedValue();
         }
         // TODO: Maybe findAssignedValueByStub() should become a part of the PyTargetExpression
         // interface
         else if (elt instanceof PyTargetExpressionImpl) {
           assigned_from = ((PyTargetExpressionImpl) elt).findAssignedValueByStub(context);
         }
         if (assigned_from instanceof PyReferenceExpression) {
           if (visited.contains(assigned_from)) {
             break;
           }
           visited.add(assigned_from);
           seeker = (PyReferenceExpression) assigned_from;
           if (seeker.getQualifier() != null) {
             qualifiers.add(seeker.getQualifier());
           }
           continue SEARCH;
         } else if (assigned_from != null)
           ret = new QualifiedResolveResultImpl(assigned_from, qualifiers, false);
       } else if (ret == null && elt instanceof PyElement && target.isValidResult()) {
         // remember this result, but a further reference may be the next resolve result
         ret =
             new QualifiedResolveResultImpl(
                 elt, qualifiers, target instanceof ImplicitResolveResult);
       }
     }
     // all resolve results checked, reassignment not detected, nothing more to do
     break;
   }
   if (ret == null) ret = EMPTY_RESULT;
   return ret;
 }
 @NotNull
 private static List<PyType> getIndexTypes(
     @NotNull PySubscriptionExpression expression, @NotNull Context context) {
   final List<PyType> types = new ArrayList<>();
   final PyExpression indexExpr = expression.getIndexExpression();
   if (indexExpr instanceof PyTupleExpression) {
     final PyTupleExpression tupleExpr = (PyTupleExpression) indexExpr;
     for (PyExpression expr : tupleExpr.getElements()) {
       types.add(getType(expr, context));
     }
   } else if (indexExpr != null) {
     types.add(getType(indexExpr, context));
   }
   return types;
 }
 @Nullable
 private static PyType getGenericConstructorType(
     @NotNull PyFunction function, @NotNull Context context) {
   if (PyUtil.isInit(function)) {
     final PyClass cls = function.getContainingClass();
     if (cls != null) {
       final List<PyGenericType> genericTypes = collectGenericTypes(cls, context);
       final List<PyType> elementTypes = new ArrayList<>(genericTypes);
       if (!elementTypes.isEmpty()) {
         return new PyCollectionTypeImpl(cls, false, elementTypes);
       }
     }
   }
   return null;
 }
  @Nullable
  public Ref<PyType> getParameterType(
      @NotNull PyNamedParameter param, @NotNull PyFunction func, @NotNull TypeEvalContext context) {
    final PyAnnotation annotation = param.getAnnotation();
    if (annotation != null) {
      // XXX: Requires switching from stub to AST
      final PyExpression value = annotation.getValue();
      if (value != null) {
        final PyType type = getType(value, new Context(context));
        if (type != null) {
          final PyType optionalType = getOptionalTypeFromDefaultNone(param, type, context);
          return Ref.create(optionalType != null ? optionalType : type);
        }
      }
    }

    final String paramComment = param.getTypeCommentAnnotation();
    if (paramComment != null) {
      return Ref.create(getStringBasedType(paramComment, param, new Context(context)));
    }

    final String comment = func.getTypeCommentAnnotation();
    if (comment != null) {
      final PyTypeParser.ParseResult result =
          PyTypeParser.parsePep484FunctionTypeComment(param, comment);
      final PyCallableType functionType = as(result.getType(), PyCallableType.class);
      if (functionType != null) {
        final List<PyCallableParameter> paramTypes = functionType.getParameters(context);
        // Function annotation of kind (...) -> Type
        if (paramTypes == null) {
          return Ref.create();
        }
        final PyParameter[] funcParams = func.getParameterList().getParameters();
        final int startOffset = omitFirstParamInTypeComment(func) ? 1 : 0;
        for (int paramIndex = 0; paramIndex < funcParams.length; paramIndex++) {
          if (funcParams[paramIndex] == param) {
            final int typeIndex = paramIndex - startOffset;
            if (typeIndex >= 0 && typeIndex < paramTypes.size()) {
              return Ref.create(paramTypes.get(typeIndex).getType(context));
            }
            break;
          }
        }
      }
    }
    return null;
  }
 /** @param self should be this */
 @NotNull
 private static List<PyAssignmentStatement> findAttributesStatic(@NotNull final PsiElement self) {
   final List<PyAssignmentStatement> result = new ArrayList<>();
   for (final PyAssignmentStatement statement :
       new PsiQuery(self).siblings(PyAssignmentStatement.class).getElements()) {
     for (final PyQualifiedExpression targetExpression :
         new PsiQuery(statement.getTargets()).filter(PyQualifiedExpression.class).getElements()) {
       final PyExpression qualifier = targetExpression.getQualifier();
       if (qualifier == null) {
         continue;
       }
       final PsiReference qualifierReference = qualifier.getReference();
       if (qualifierReference == null) {
         continue;
       }
       if (qualifierReference.isReferenceTo(self)) {
         result.add(statement);
       }
     }
   }
   return result;
 }
 private static PyType getTypeByControlFlow(
     @NotNull String name,
     @NotNull TypeEvalContext context,
     @NotNull PyExpression anchor,
     @NotNull ScopeOwner scopeOwner) {
   PyAugAssignmentStatement augAssignment =
       PsiTreeUtil.getParentOfType(anchor, PyAugAssignmentStatement.class);
   try {
     final PyElement element = augAssignment != null ? augAssignment : anchor;
     final List<ReadWriteInstruction> defs =
         PyDefUseUtil.getLatestDefs(scopeOwner, name, element, true);
     if (!defs.isEmpty()) {
       PyType type = defs.get(0).getType(context, anchor);
       for (int i = 1; i < defs.size(); i++) {
         type = PyUnionType.union(type, defs.get(i).getType(context, anchor));
       }
       return type;
     }
   } catch (PyDefUseUtil.InstructionNotFoundException ignored) {
   }
   return null;
 }
 @Nullable
 private Modifier getWrappersFromStub() {
   final StubElement parentStub = getStub().getParentStub();
   final List childrenStubs = parentStub.getChildrenStubs();
   int index = childrenStubs.indexOf(getStub());
   if (index >= 0 && index < childrenStubs.size() - 1) {
     StubElement nextStub = (StubElement) childrenStubs.get(index + 1);
     if (nextStub instanceof PyTargetExpressionStub) {
       final PyTargetExpressionStub targetExpressionStub = (PyTargetExpressionStub) nextStub;
       if (targetExpressionStub.getInitializerType()
           == PyTargetExpressionStub.InitializerType.CallExpression) {
         final QualifiedName qualifiedName = targetExpressionStub.getInitializer();
         if (QualifiedName.fromComponents(PyNames.CLASSMETHOD).equals(qualifiedName)) {
           return CLASSMETHOD;
         }
         if (QualifiedName.fromComponents(PyNames.STATICMETHOD).equals(qualifiedName)) {
           return STATICMETHOD;
         }
       }
     }
   }
   return null;
 }
 @NotNull
 private static List<PsiElement> tryResolving(
     @NotNull PyExpression expression, @NotNull TypeEvalContext context) {
   final List<PsiElement> elements = Lists.newArrayList();
   if (expression instanceof PyReferenceExpression) {
     final PyReferenceExpression referenceExpr = (PyReferenceExpression) expression;
     final PyResolveContext resolveContext =
         PyResolveContext.noImplicits().withTypeEvalContext(context);
     final PsiPolyVariantReference reference = referenceExpr.getReference(resolveContext);
     final List<PsiElement> resolved = PyUtil.multiResolveTopPriority(reference);
     for (PsiElement element : resolved) {
       if (element instanceof PyFunction) {
         final PyFunction function = (PyFunction) element;
         if (PyUtil.isInit(function)) {
           final PyClass cls = function.getContainingClass();
           if (cls != null) {
             elements.add(cls);
             continue;
           }
         }
       } else if (element instanceof PyTargetExpression) {
         final PyTargetExpression targetExpr = (PyTargetExpression) element;
         // XXX: Requires switching from stub to AST
         final PyExpression assignedValue = targetExpr.findAssignedValue();
         if (assignedValue != null) {
           elements.add(assignedValue);
           continue;
         }
       }
       if (element != null) {
         elements.add(element);
       }
     }
   }
   return !elements.isEmpty() ? elements : Collections.singletonList(expression);
 }
 @Nullable
 private String extractReturnType() {
   final String ARROW = "->";
   final StructuredDocString structuredDocString = getStructuredDocString();
   if (structuredDocString != null) {
     return structuredDocString.getReturnType();
   }
   final String docString = getDocStringValue();
   if (docString != null && docString.contains(ARROW)) {
     final List<String> lines = StringUtil.split(docString, "\n");
     while (lines.size() > 0 && lines.get(0).trim().length() == 0) {
       lines.remove(0);
     }
     if (lines.size() > 1 && lines.get(1).trim().length() == 0) {
       String firstLine = lines.get(0);
       int pos = firstLine.lastIndexOf(ARROW);
       if (pos >= 0) {
         return firstLine.substring(pos + 2).trim();
       }
     }
   }
   return null;
 }